In hybrid vehicle designs, vehicle transmission input torque may be supplied as a sum of engine torque and an electric motor torque dependent on vehicle operation conditions. As an example, during initial vehicle acceleration, driveline torque to a transmission impeller may be supplied almost completely by the motor, and then motor torque may be reduced as increased engine torque becomes available. In this way, engine torque and motor torque can be varied while providing the desired demand torque. However, if there are errors in estimated engine torque and/or motor torque, the driver may notice a change in vehicle acceleration as the ratio of engine torque to motor torque changes. Therefore, it may be desirable to accurately estimate engine torque and motor torque.
The inventors have recognized the above issues and have developed a method of controlling hybrid engine torque output comprising: during a transient torque increase responsive to a change in desired powertrain output torque, adjusting engine output torque and motor output torque responsive to the change in desired powertrain output torque, and further adjusting motor output torque in response to a torque converter impeller speed response.
By responding to a torque converter speed response, it may be possible to provide a desired torque converter impeller torque when motor torque and engine torque are varying so that a vehicle driveline does not experience unexpected increases or reductions in driveline torque. For example, motor output torque may be adjusted in response to torque converter speed response so that a desired torque converter impeller torque may be provided even in the presence of engine torque estimation errors. Further, motor torque may compensate for engine torque estimation errors, and an engine torque estimate may be updated or adapted based on an amount of a motor torque adjustment. In this way, a more accurate actual torque converter impeller torque may be provided from a desired torque converter impeller torque.
The present description may provide several advantages. Specifically, the approach may reduce torque disturbances in a vehicle driveline. Further, the approach may improve hybrid vehicle efficiency by allowing the engine and/or motor to operate at design conditions. Further still, the approach may provide some compensation for driveline degradation as the vehicle ages.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.